I would like to share with you our new paper that just got published in January volume of Icarus journal.
The most exciting part of this paper is that HiRISE detected some new troughs in Martian polar areas. The troughs were not visible when the HiRISE observed those locations for the first time in Martian Years (MY) 28 and 29. But when we have commanded HiRISE to take repeated observations in MY 30 and 32, we were rewarded with images of new features that you can see in the animated image below.
The troughs are really small: the whole image is less than 200 m across, while the new troughs are only up to 1 m wide. The total length of them reaches 582 m thanks to their multiple branches.
The new troughs, large enough for HiRISE to detect, are created under the current climate condition – and this is really a big deal. They do look much like spiders: they have different tributaries and resemble the dendritic nature of the large spiders. And they are developing. In turn this means that the large spiders might be developing right now as well. We are still waiting to see topographical changes on the large and fully developed spiders, but we know now that the process is able to erode away quite some ground material. For example, the volume of the material that was moved to create the troughs in the image above is 24 m², they were created over 3 MY, meaning, the process moved 8 m² yearly only in this one example.
The erosion rates like this lets us evaluate the age of the large spiders. They take amazing 1.3 thousands Martian years! It is a long time for a human being, but it is really just a blink of an eye for a geological feature.
We are continuing to monitor these locations to check if these troughs will not be erased in the next years. It well may happen because the new spiders are located very close to the dune fields, and moving sand is capable to cover or sand-blast these small topographical features barely in a year.
I once did a very similar search with Mars Orbital Camera (MOC) images. The camera worked on Mars Global Surveyor from 1997 to 2006. It had 2 sub-systems: a wide-angle camera and a narrow angle camera. The narrow angle camera obtained grayscale images with resolution from 1.5 to 12 m per pixel. It was just good enough to resolve larger spiders and fans.
In 2004 I looked through all MOC images that existed at the time and were located south of latitude -75º. I was hunting for spiders. The result is a list of MOC images that feature spiders and it is now being added to Integrated Database of Planetary Features. It will be available as a layer in JMARS system in a couple of months.
You can see Spiders map on Database of Planetary Features.
When we have a catalog of CTX images with spiders created by you, we will also integrate it into this database! Then everyone can easily navigate around different locations of spider terrains.
I want to talk why we created the new project Planet Four: Terrains if we have Planet Four already.
The very high resolution images of HiRISE camera are really impressive and one might think that there is no reason to use a camera with lower resolution anymore. Wrong!
First, high resolution of HiRISE image means large data volume. To store on-board and to download large data from MRO spacecraft to Earth is slow (and expensive) and this means we are always limited in the number of images HiRISE can take. We will never cover the whole surface of Mars with the best HiRISE images. Sadly. so we use different cameras for it. Some – with very rough resolution and some – intermediate, like context camera (CTX). We can use CTX, for example, to gain statistics on how often one or the other terrain type appears in the polar areas. This is one point why Planet Four: Terrains is important.
Second, because HiRISE is used for targeted observations, we need to know where to point it! And we better find interesting locations to study. We can not say “let’s just image every location in the polar regions!” not only for the reason 1 above, but also because we work in a team of scientists and each of them has own interests and surely would like his/her targets to be imaged as well. We should be able to prove to our colleagues that the locations we choose are truly interesting. To show a low-resolution image and point to an unresolved interesting terrain is one of the best ways to do that. And then, when we get to see more details we will see if it is an active area and if we need to monitor it during different seasons.
Help us classify terrains visible in CTX images with Planet Four: Terrains at http://terrains.planetfour.org
Dear Mars Explorers,
Today, June 18 at about 6pm UTC Mars completes yet another turn around the Sun and its calendar starts with brand new year 33 at Ls=0°!
HAPPY NEW MARTIAN YEAR EVERYONE!
You might remember that the last New Martian Year was at Earth’s date July 31, 2013. The shift to June 18 is due to the difference of Martian and Earth year length: the Mars year is 687 Earth days, meaning it’s 43 days shorter than 2 Earth years.
New Year on Mars starts with the spring equinox in the northern hemisphere. This means it is fall right now in the southern hemisphere in the areas that you are analyzing. All the ice from previous winter is long gone by now, the surfaces are inactive. The times of darkness become longer and longer and soon come long winter nights. At some locations there will be polar nights, when the Sun stays below the horizon for more than a day. These times are cold and CO2 will start to condense on the surface. First in some record-cold shadowed places and then all over southern polar areas. And it might even snow CO2 flakes!
I leave you with this simulated Martian analemma – the image of the Sun in the Martian sky taken at the same local time during the whole Martian year. Slightly less bright, the simulated Sun is only about two thirds the size as seen from Earth, while the Martian dust, responsible for the reddish sky of Mars, also scatters some blue light around the solar disk. On Earth an analemma is a figure-8, while on Mars it is a tear-drop because of a different relationship between orbit eccentricity and its rotational axis tilt than on Earth (see this excellent blog post by Ethan Siegel explaining analemma details).
Right now the Sun on Mars is near the middle of this teardrop and moving towards the narrower tip. In about 1 Earth year the spring will come to Southern hemisphere and the southern polar activity will start again, new fans and blotches will appear giving us more data to investigate!
Thank you for helping us with this investigation!
Let us celebrate by classifying an image or two! Happy New Year!
Good news: our wonderful development team has added new feature that many of our volunteers have asked for! Now you can see north azimuth, sub-solar azimuth, phase angle, and emission angle on the Talk pages directly. You can see an example here. These angles give you information about how HiRISE took the image and where the Sun was at that moment.
To understand what those angles are, here is an illustration for you:
You see how the MRO spacecraft flies over the surface while HiRISE makes an image. The Sun illuminates the surface .
Consider a point on the martian surface P.
Emission angle: HiRISE does not necessarily look at point P straight down, i.e. the line connecting point P and HiRISE has some deviation from vertical line – it is noted as angle e on the sketch. This is emission angle. It tells you much we tilted spacecraft to the side to make the image.
Phase angle: Because all the images you see in our project is from polar areas, the Sun is often low in the sky when HiRISE observes. To get an idea on how low, we use phase angle – it is the angle between the line from Sun to the point P and line from point P to the HiRISE. It is noted φ in the sketch. The larger phase angle is, the lower the Sun in the sky, the longer are the shadows on the surface.
Sub-solar azimuth: To understand what is the direction towards the Sun in the frame of HiRISE image, we use sub-solar azimuth. In any frame that you see on our project it is an angle between horizontal line from the center of the frame towards right and the Sun direction. It is counted clock-wise. The notation for it in the sketch is a.
North azimuth: The orbit of MRO spacecraft defines orientations of HiRISE images. North azimuth tells us direction to the Martian north pole. In the frame of an image it’s counted same as sub-solar azimuth, i.e. from the horizontal line connecting center of the frame and its right edge in the clock-wise direction.
I hope this helps you enjoy exploring Mars with HiRISE!
It is really-really tough to get funding to do research. You have to have an idea to do something really new and important, something that will be interesting and useful. You need to gather a team that can do it. Then you have to write a proposal to explain your idea and to convince other scientists that this project is worth pursuing. And you’ll be competing with other projects for the limited budget pot. It was even tougher than usual this year for planetary research at NASA: only 14% of all submitted projects got funding.
But we did!
A little project that utilizes the data from Planet Four will be funded by NASA so that we can compare directions of winds mapped by our citizen scientists (via fans, of course!) to the prediction of martian climate models!
This is so very exciting!
We have a great team here and I am convinced this project will be a great success! Thanks NASA and thanks all of our helpers on planet4!
Mars is slowly coming towards summer in the southern hemisphere and the same time to the perihelion on its orbit around the Sun.
This project is focused on fans in Martian southern polar areas. But do you know why southern? There are similar features in the northern polar areas, but they are much smaller. In fact, for quite some time scientists believed that the kind of activity that produces dark fans and blotches (cold CO2 jets) did not happen in the north. They thought so, because they could not see any signs of it in the north. Or better to say, they could not resolve it. At that time, from 1996 to 2005, the images of martian ground were coming from the Mars Orbiter Camera (MOC) and their highest ground resolution was 1 m/pix. It is enough to resolve large southern fans, but just not enough for the northern smaller ones! Only when HiRISE came around and imaged northern dunes, we saw that there are blotches and fans too. So, why the scales of them are so different? There might be several explanations. Below I will offer you one, which is probably the first to think about.
Martian seasons in southern and northern hemispheres are not equal.
Mars has elliptical orbit, its eccentricity is 0.0934 (e = 0 would be a circle). It is small, but in the planetary scale it takes Mars some 42 million kilometers closer to the Sun in its closest approach than in the furthest position on the orbit. The closest approach is called perihelion, from Greek “near the Sun”. It happens during summer in the southern hemisphere.
So, Mars is closer to Sun when it is summer in the south – this means during southern summer it gets more solar energy than during northern. Unlike our Earth, Mars does not have a huge water reservoir of the oceans to dampen temperature variations. These 2 facts together lead to that southern summer is hotter than the northern. But how does this affects what happens in spring? In two ways: first, the amplitude of change from cold dark winter to hot bright summer is larger in the south. And second: Mars is moving faster on its orbit when it is closer to perihelion. So the changes happen faster!
Every day in spring the amount and strength of sunshine increases. In the north this increase is steady but slow. It probably makes seasonal ice layer subliming steadily from the top faster than creating under-ice gas cavities that burst and create cold CO2 jets and associated fans. While in the south every day energy increase is more like a jump: getting these bursts makes for higher probability of under-ice explosions. And lets us observe beautiful fans!
We have recently started showing you data from a new location! Have you noticed?
This new place is called Ithaca. It is located at lat =-85.2, lon = 181.401. Unlike Inca City (our most recent focus), this is a flat area, no considerable slopes are present here. Ithaca is located in the middle of this elevation map:
You see, that the red area has maximum elevation change of less than 80 meters. In the absence of slopes, we can say more confidently that the fans here are result of interaction of dusty CO2 jets with winds and not gravity simply pulling sand downhill. Winds direct dust and sand particles after they are lifted up into the atmosphere by the jets. It is very striking, that the fans look very similar in several consequent years of HiRISE observations. The usual year in Ithaca looks like this:
This is a mini-series of HiRISE images from early spring (a) progressing to late spring via (b) to (c) and finally to (d). Fist images that HiRISE returns each spring show large dark fans with the similar opening angles and similar directionality every year. This tells us that there is few variation in local weather from year to year.
When spring progresses, fans extend, later blue fans appear, and sometimes they take over most of the surface! Like in figure (c) – whole area is blue apart from really dark fans. This is one of the mysteries of Ithaca – we know from spectrometers, that those blue fans are fresh CO2 frost, but how comes fresh frost appears on the sides of the dark fans? Dark surface is warmer when exposed to sunlight and must prevent CO2 from forming there.
Another Ithaca mystery is its fan sizes. Here the fans grow to be huge: you see the scale bar on the first image? That is 100 m and the fans on the figure (d) are 2-3 times that long. It is larger then in most of other polar locations. For example Inca City, that must be familiar to you by now, has fans of only tens of meters. Currently scientist do not have models that is able to explain how such big fans form.
If you carefully compare left and right frames of the figure below, you can see quite some new fans appearing in the right frame.
Scientists would really like to know, how many of those appear each day and how big are they compared to the old fans. In this example new fans look small, but this is only one tiny area from Ithaca. To make a clear statement we really need to count them and outline their sizes. That is why Ithaca is now waiting for you to get marking!
About a week ago our colleague and a resident polar scientist on the Mars Climate Sounder (MCS) science team Dr. Paul Hayne wrote this Planetary society blog post. He talks about CO2 snowing on Mars! If you are interested to know why we think that it snows dry ice on Mars or what shape CO2 snowflakes are, go check it out! And let us know your thoughts on how it affects the areas that you are helping us to analyze!
Dear Mars Explorers,
Today marks the start of a new Martian year. The Planet Four team wishes everyone a very Happy New Year!
That’s right, today July 31 2013 on Mars, Year 31 turns into New 32 Year. As a Martian year, (a complete 668 days around the Sun) is nearly twice longer than the Earth’s, it is a rather special event. Time to celebrate!
The counting of martian years started on April 11, 1955, this was the date of Ls=0 back in that time. Since then the moment when Mars completes its turn around the Sun shifted for us, Earthlings, from April to July. It will continue to shift further, because martian year is close but not precisely equal to 2 terrestrial years. To give you a perspective, Planet4 is 7 months old now, this means, only a bit older than a quarter of a martian year!
In contrast to Earth, New Year comes to Mars when northern hemisphere is in spring, and it is fall in southern hemisphere. For areas that you are analyzing this means rather boring time: all the ices are gone from the surface and the ground stands bare and inactive. But even inactive, the scenery is still very impressive. For the New Year celebration we decided to share with you a glimpse into a very fresh HiRISE image. It was taken only a week ago. Some of you might recall the area you were studying! Now there are only dim reminders of the fans that you are marking for us so efficiently.
Thank you for doing it with us and lets celebrate by classifying an image or two! Happy New Year!